The long term objective of this propose project is to investigate how childhood health are determined, how childhood health can affect adulthood health and later life chances, and how these are translated into the next generation well-being. The goal of the proposed study is to investigate relationships between birth weight and childhood asthma and how environment and experiences during childhood can moderate that relationship. There are three specific Aims of the proposed study: Aim I: To estimate the association between low birth weight and the risk of asthma among children (0-17) net of observable family and community backgrounds by using the nationally representative data. Aim II: To estimate the association between low birth weight and the risk of asthma among children by using a sibling model to control for unobservable background factors. Aim I To estimate the impacts of changing maternal risk behavior (such as smoking), family structure, residence area, and other familial and environmental factors during childhood on the risk of asthma by using panel models. Aim IV: To examine whether the estimated association between low birth weight and asthma is moderated by potential changes in disadvantage, whether in parental risk behavior, family structure, residence area, or other familial and environmental factors during childhood by using sibling models. To examine whether the estimated association between low birth weight and asthma is moderated by disadvantaged changes in parental risk behavior, family structure, residence area, and other familial and environmental factors during childhood by using sibling models. Two nationally representative data are used National Health Interview Survey (NHIS) and the National longitudinal Survey of Youth 1979 cohort children Data (NLSY79-CD). By using the NHIS data, the association between low birth weight and the chance of asthma among children could be investigated. With the NLSY-CD data, panel data models and sibling models are applied to control for unobserved factors for children and their siblings.